The stability of the mammalian axial skeleton is determined by the interaction of bony elements, connective tissues, and ligaments. This research project will examine axial stability and instability in a mammalian system that naturally exhibits both conditions. Specifically, this project will use a novel animal model, the bottlenose dolphin (Tursiops truncatus), to investigate the role morphology plays in determining the mechanics of spinal instability. The axial skeletons of fetal and neonatal dolphins are characterized by extreme instability, which disappears in response to normal growth patterns after a few weeks. This project will document the changing stability of the dolphin backbone in conjunction with the morphological growth patterns that occur simultaneously. The stability of the dolphin axial skeleton will be determined used a combination of in vitro mechanical tests and in vivo kinematic methods. These data will be correlated with quantitative morphological data, both gross and histological, from a developmental series of bottlenose dolphins. Ultimately, this research proposal aims to identify the morphological features that contribute to structural stability in the developing mammalian backbone. The results from this study may shed light on casual factors associated with observed pathologies such as lumbar instability and idiopathic scoliosis, as well as identifying structures that protect the spinal cord from damage due to excessive deformations.